Free piston compressor and control therefor



0 e. A. MUELLER, JR 2,494,573

FREE PISTON COMPRESSOR AND QONTR OL THEREFOR Filed May 16, 1947 2Sheets-Sheet 1 INVENTOR. GEunQzAMusLLzn, J12.

ATTYS.

1950 G. A. MUELLER, JR 2,494,573

FREE PISTON COMPRESSOR AND CONTROL THEREFOR Filed llay 16, 1947 2Sheets-Sheet 2 I Q *l IN VEN TOR.

IE1 LT Saunas A. MUELLER, JR.

"QMQM Patented Jan. 17, 1950 I 2,494,573

UNITED STATES PATENT OFFICE 2.494573 FREE PISTON GODIPRESSOR AND CONTROLTHEREFOR George A. Mueller, Jr., Hamilton, Ohio. "signer, by Inesneassignments, to Lima-Hamilton Corporation. Hamilton, Ohio, a corporationof Application Mil! 16, 1947, Serial No. 748,591 12 Claims. (Cl. 123-48)This invention relates to free piston internal merits by racks 28-29which extend toward each combustion engines and is particularly directedto other from connectors 30 on each crosshead l2. a combinedengine-compressor unit and a control The racks are thus of short lengthand are so distherefor. posed that they do not pass between chambers Theprimary object oi the invention is to procontaining air at diirerentpressures. The necesvide a free-piston engine-compressor and a consityfor packing glands around the racks is thus trol therefor which resultsin the extent of the eliminated. The usual synchronizin pinion 32 strokeor the power and compressor pistons remeshes with both racks andreciprocates on a maining substantially constant over the operathub orshaft 34 extending from the center oi the ingrange. m exterior oi thepower cylinder or at some other Another object of the invention is toprovide a convenient location. ontrol for a free-pi on n ineompr or niAir is drawn into the unit to be compressed for in Which p e hydraulic11 e ay are scavenging the engine cylinder as well as for use ope a ed yan engine r at the e ds of a strok in the receiver 6. A common intakemanifold of p e in e l e e ay n n 0 36 is provided which communicateswith the at- 8 the amount sv imparted o the mosphere through appropriatefilters (not shown) cy l a ch e d of he stroke of the pis n and withboth ends oi the cylinder in which com- Still another object of theinvention is to propressor pistons It operates. This cylinder is, asvide a device of the above character in which the above stated, dividedinto an inner part 22 in load n the engine parts added y h control ewhich scavenging air is compressed, and an outer ments s n zed and w his pensive to part 24 in which air is compressed and led to theconstruct and maintain. receiver 6. The passage between the intake Otherobjects and advantages of the invention manifold and the scavenging aircompressing will become app ent m the fol w n s cicylinder is designated38 and a plurality oi simfication, reference being had to theaccompanying ilar, self contained check valves Ill control the drawingsin which: passage of air from manifold to cylinder. At one ure l is adia mm c S e elevation a side the check valves 40 open toward thecylinder free piston engine-compressor unit with par s to admit air onthe intake stroke, and at the other broken away to show he rel ive poitions occuside or the cylinder, valves 4| control the outward pied bythe several control elem x. 3 18 flow of air from the cylinder 22 to ascavenging rammatic View, partly in c the unit airheader 2 whichcommunicates with the power c nve y p rated. and 8- 3 s a omposite Airis drawn into the compressor cylinder diagrammatic sectional view oi theseveral conthrough i t k ports 44 and discharged through trol elements.ports 46 to the header 2 on the rearward stroke Referring to the dranae. nd rti r y o of compressor piston It. From the compressor Figs. 1and 2, the present inven n 1 h wn apheaders the air passes check valve 8and enters p d to Iree piston compressor unit 01' the opreceiver 6 fromwhich it may be utilized in any posed piston type. At the ends or theunit are known manner, headers 2 and l which communicate with a com-Bounce cylinders 26 operate as chambers in men compressed air trunk Iand, thereby. wi which energy is stored during the outward stroke areceiver an inwardly ning check Valv l of the pistons to be utilized tocause return of the being disposed at the entrance to the receiver.pistons to firing position. The major portion 0t Each of the opposedpistons comprises a power the air in these chambers is preIerabLvcontained piston Ill, 01' appropriate diameter, then a stem in annularside chambers 21, although a straight, or crosshead portion 12 to whichis connected a continuous chamber may be used. The bounce compressorpiston N and finally a bounce piston chambers are closed spaces to whichair is added it. Cylinders of the proper diameter are assoor withdrawnas hereinafter described. It will be ciated with each of the pistonsections and in 50 appreciated that the extent of the inward strokeignated 22; the compressor cylinder 24 and the stroke may be lengthenedor shortened by changbounce cylinder 26. ing the quantity 01 air in thebounce chambers The pistons are synchronized in their moveas and itsinitial pressure.

angers control m- The present invention provides a working tem which isactuated by th pistons, through the synchronizing racks and m to bedescribed. that controls the supply of fuel to the firing cylinder andthe air in the bounce chambers in such a manner that the stroke of thepistons remains substantially constant throughout the working range.

A dump valve ii is provided. either in the compressed air trunk i or ina by-pass conduit II leading from the trunk to a convenient location.Valve II may be operated by any suitable means such as a piston 52working in a cylinder 51 against the tension of a spring Bl. A pilotvalve 55 operated by air from the receiver admits air at receiverpressure to the front face of piston 52 whenever the receiver pressurereaches a predetermined level which may be adjusted by varying the forceof a spring 58 against which pilot valve it moves toward open position.Suitable air passages are provided in the valve body to admit andexhaust air to and from cylinder 53, the vent passage being designated51 and the passage by which air enters from the receiver 58. Thesepassages are, of course, opened and closed by the pilot valve 55. Itwill thus be apparent that when the receiver is charged with air at itsintended pressure the dump valve is opened and the load on thecompressor is reduced to only that required to maintain the pistons inoperation, nearly all of the energy taken from the cycle on theoutstroke of the pistons being stored in the air in the bounce chambersand returned to the cycle by expansion on the next succeeding instroke.During the period that the receiver is full of air at its intendedpressure, check valve 8 functions to prevent this pressure from actingagainst the compressor and prevents the escape of air from the receiver.

Fuel control is accomplished by a device operating in response to theextent of the outstroke of the pistons. The engine fuel pump is showndiagrammatically at 60 and includes the usual adjusting rack 62 to whichis connected a piston 64 operating in a cylinder 68 and biased to the oposition by a spring 08. Pressure at the rear of the piston moves therack in a direction such that more fuel is iniected at each stroke ofthe fuel pump plunger. An adjustable needle valve III is inserted in thebleed passage from cylinder 69 so that the rate of response of the fuelcontrol may be changed at the selection of the operator. The fuel pumpmay be operated in any suitable manner as by a cam ii rocked by a rodBl.

Shaft ill on which the synchronizing pinion is mounted is continued outfrom the side of the engine and carries a second pinion 12 whichcooperates with an arcuate rack ll formed on the end of a lever I6pivoted at 18 and carrying adjustable actuating members an, 8| at itsshort end. It will thus be seen that as pinion 12 rotates the actuatingmembers 8|! and 8! reciprocate about pivot point III with the extent oftheir reciprocation determined by the extent of the rotation of pinion12. Rod 63 may be operated by lever 16 to move fuel cam 6|.

Actuating member 8|, in its reciprocation, abuts against a stem 82 of apiston type valve 83 the enlarged rear end of which operates in a dashpot cylinder M, the valve being biased to open position by a spring 85.Valve 83 controls the flow of oil or other actuating fluid between aconduit 86 and a conduit 88. Conduit It is fed with oil under pressureby a pump I and conduit ll communicates with cylinder II at the fuelpump. Thus. as valve ll moves to such a position that its reduced area.designated 82, opens communication between conduits It and 88 a smallquantity of oil will pass the valve and enter cylinder 6. While thevalve remains closed cylinder 68 tends to driiin into a bleed passage 9!around needle valve II. In the normal operation of the engine the strokeis adjusted so that valve 88 opens periodically in an amount suflicientto move the fuel rack 62 to the proper adjusted position. If the enginestroke is too long at the outer end. valve 8 is closed by abutment ofactuating member it against stem 82 and less fuel is injected at the Wnext stroke since the supply of oil is cut off to cylinder 65 and therack tends to drift toward the off position. The sensitivity of thedevice can be changed by adjustment of needle valve Ill so thatpersistent trends are followed rather than individual overstrokes.

To control the extent of the instroke of the pistons a valve 86 providedwith an abutment I8 is provided to control the fiow of oil betweenpassages Hill and MI. Passage ill communicates with pump 90 and passagelti communicates with a bounce air governor I02. Valve Ii may beconveniently controlled by a spring ill acting on its rear end andworking in a I05. The valve passage is designated I" and, as in the caseof valve 83, the unit is biased to open position and is moved to cut-oi!position by abutment of actuating element against stem 98.

The bounce air governor I02 may take any suitable form by which airunder pressure is admitted to or bled from the direct bounce chambersII. A common passage ma leads to these chambers and enters the body ofgovernor Hit in a common conduit llfl. Air under pressure is supplied tothe governor ill: by a conduit III which connects to an air storagebottle H4 having the usual shut-01f valve H5 at its outlet. A vent pipeH6 is also connected in the governor body.

Governor 802 contains a slide valve I20 of the piston type urged in onedirection by a spring ill and in the opposite direction by oil underpressure entering from conduit HH and acting against the face of thepiston valve In. Oil thus entering bleeds past an adjustable needlevalve in to a drain passage I24 so that the rate of bleed. and thus therate of actuation of the valve I, may be easily controlled. It will beseen that in the position to which the valve I" is urged. in i theabsence of pressure on its face, communication is opened between passagelill which leads to the direct bounce cylinders and the vent passage IIBthrough an upper communicating passage IIB formed in the body N12. Thepressure in the direct bounce chambers is thus reduced.

when oil under pressure enters through pipe ltl and acts on the face ofvalve I20 moving it against its spring, the vent passage H6 is closedand communication is opened between air line I I 2 and the chargingbottle H4 and passage lit to the direct bounce chambers thus increasingthe pressure of air in these chambers. As the pressure of the air in thedirect bounce chambers increases the extent of the instroke of thepistons is increased and, conversely the lower pressure in the directbounce chambers permits a shorter lnstroke of the pistons to be made.The control thus results in valve I20 hunting between a position ofcharging and venting the direct bounce dash-pot cylinder asses-rschambers, with the rate of change being governed largely by the settingof needle valve III. Persistent trends toward an increase or decrease inthe length of stroke of the pistons will be followed where individualdiflerences in the strokes do not necessarily result in a change 'in thepressure in the direct bounce chambers.

In operation the compressor works against a predetermined receiverpressure and so long as the dump valve in the receiver line remainsclosed the compressor is under load and suilicient fuel is injected tocause the pistons to compress air to a pressure high enough to overcomethe check valve 8 in the compressed air header. When the dump valveopens by reason of the desired receiver pressure being attained, thecheck valve 0 remains closed and the compressor idlesat full stroke andjust enough fuel is iniected to maintain the proper stroke length.Should the compressor begin to understroke the fuel will be increased byreason of the movement of valve 03 to a position such that oil passesinto conduit 88 and hence to cylinder 66 adjacent the fuel rack.

Should the compressor then tend to overstroke' the supply of oil toconduit 00 is cut off. the contents of cylinder 66 bled past valve 10 toline 94 and the rack 62 drifts toward cut-oi! position.

At the inner end of the stroke the proper piston position is maintainedby increasing or decreasing the pressure in the direct bounce chambers.As the load on the compressor increases and the amount of fuel injectedat each stroke is, therefore, increased the pressure on the directbounce chambers tends to build up and thus forces the pistons closertogether at the exact compression strokes. If this tendency goesobjectionably far. actuating element 00 strikes the stem 98 of valve 96which then operates to cut off communication between passages I00 and INso that fluid operating against the front face of piston valves I20 canbleed past needle valve I22 into the drain line I24. The valve I20 thendrifts to the left under the influence of spring III and openscommunication, through passage I28, between the direct bounce line I I0and the vent line I It. The direct bounce spaces are thus vented to a.lower pressure and the pistons urged together less forcibly. The balanceof operation is thus restored and succeeding end strokes of the pistonswill be of the proper length. This venting continues until actuatingelement 00 no longer strikes stem 98 and communication to the oilpressure line I00 is again restored and valve I20 moved to a positionsuch that the venting of the direct bounce chambers is stopped.Continued understroking causes valve I20 to move to charging positionand the direct bounce chamber pressure is increased.

It will be seen that the present invention provides a control balancewhich is capable of precise adjustment so that the length of stroke ofthe pistons will remain substantially constant, varying between limitswhich can be easily determined and maintained.

While the invention has been described in connection with a particularform and disposition of the parts it should be appreciated that numerousmodifications and changes may be made without departing from the spiritof the appended claims.

What I claim is:

1. A free piston compressor of the class described comprising, axiallyaligned power, compressor and bounce cylinders, and pistons workingtherein, a compressed air receiver, means to control the quantity offuel entering said power cylinder. mean to vary the pressure of air insaid bounce cylinders, a member reciproeated by said pistons, and spacedvalves operated by said member at each end of its stroke, one valveoperating to actuate said fuel control means and the other valveoperating said bounce air control means, whereby the stroke of saidpistons remains substantially constant.

2. A free piston compressor of the class described comprising axiallyaligned power, compressor and bounce cylinders, and pistons workingtherein, means to control the quantity of fuel entering said powercylinder, a vent for' said bounce cylinders, a source of high pressureair for said bounce cylinders, fluid operated means to place said bouncecylinders either in communication with said vent to lower the pressuretherein or with said high pressure air source to increase the pressurein said cylinders, a member reciprocated by said pistons, and spacedvalves operated by said member at each end of its stroke, one valveoperating to actuate said fuel control means and the other valveoperating said bounce air control means, whereby the stroke of saidpistons remains substantially constant.

3. A free piston compressor of the class described comprising axiallyaligned power, compressor and bounce cylinders, and pistons workingtherein, a fuel injector, fluid operated means to control said injectorto increase or decrease the quantity of fuel entering said powercylinder, a vent for said bounce cylinders, a source of high pressureair for said bounce cylinders, fluid operated means to place said bouncecylinders either in communication with said vent to lower the pressuretherein or with said high pressure air source to increase the pressuretherein, a member reciprocated by said pistons, and spaced valvesoperated by said member at each end of its stroke, one valve operatingto actuate said injector control means and the other valve operatingsaid bounce air control means, whereby the stroke of said pistonsremains substantially constant.

4. A free piston compressor of the class described comprising axiallyaligned power, compressor and bounce cylinders, and pistons workingtherein, a compressed air receiver in communication with said compressorcylinders, a check valve controlling the passage of air to saidcompressed air receiver and preventing return from the receiver to saidcompressor cylinders, a by-pass to atmosphere on the compressor side ofsaid check valve, means to open said by-pass when the receiver pressurereaches a predetermined level so that the compressor operates thereafteragainst a substantially atmospheric pressure, means to control thequantity of fuel entering said power cylinder, means to vary thepressure of air in said bounce cylinders, a member reciprocated by saidpistons, and spaced valves operated by said member at each end of itsstroke, one valve operating to actuate said fuel control means and theother valve operating said bounce air control means, whereby the strokeof said pistons remains substantially constant.

5. A free piston compressor of the class described comprising, axiallyaligned power, compressor and bounce cylinders, and pistons workingtherein, a compressed air receiver in communication with said compressorcylinders, a check valve controlling the passage of air to saidcompressed air receiver and preventing return from the receiver to saidcompressor cylinders, a by-pass to atmosphere on the compressor side ofsaid check valve, means to open said by-pass when the receiver pressurereaches a predetermined level so that the compressor operates thereafteragainst a substantially atmospheric pressure, a fuel injector, fluidoperated means to control said injector to increase or decrease thequantity of fuel entering said power cylindenmeans to vary the pressureof air in said bounce cylinders, a member reciprocated by said pistons,and spaced valves operated by said member at each end of its stroke, onevalve operating to actuate said fuel injector control and the othervalve operating said bounce air control means, whereby the stroke ofsaid pistons remains substantially constant.

6. A free piston compressor of the class described comprising, axiallyaligned power, compressor and bounce cylinders, and pistons workingtherein, a compressed air receiver in communication with said compressorcylinders, a check valve controlling the passage of air to saidcompressed air receiver and preventing return from the receiver to saidcompressor cylinders, a by-pass to atmosphere on the compressor side ofsaid check valve, means to open said by-pass when the receiver pressurereaches a predetermined level so that the compressor operates thereafteragainst a substantially atmospheric pressure, means to control thequantity of fuel entering said power cylinder, a vent for said bouncecylinders, a source of high pressure air for said bounce cylinders,fluid operated means to place said bounce cylinders either incommunication with said vent to lower the pressure therein or with saidhigh pressure air source to increase the pressure in said cylinders, amember reciprocated by said pistons and spaced valves operated by saidmember at each end of its stroke, one valve operating to actuate saidfuel control means and the other valve operating said bounce air controlmeans, whereby the stroke of said pistons remains substantiallyconstant.

7. A free piston compressor of the class described comprising, axiallyaligned power, compressor and bpunce cylinders, and pistons workingtherein, a compressed air receiver in communication with said compressorcylinders, a check valve controlling the passage of air to saidcompressed air receiver and preventing return from the receiver to saidcompressor cylinders, a bypass to atmosphere on the compressor side 01'said check valve, means to open said by-pass when the receiver pressurereaches a predetermined lever so that the compressor operates thereafteragainst a substantially/atmospheric pressure, a fuel injector, fluidoperated means to control said iniector to increase or decrease thequantity of fuel entering said power cylinder, a vent for said bouncecylinders, a source of high pressure air for said bounce cylinders,fluid operated means to place said bounce cylinders either incommunication with said vent to lower the pressure therein or with saidhigh pressure air source to increase the pressure therein, a memberreciprocated by said pistons and spaced valves operated by said memberat each end of its stroke, one valve operating to actuatesaid injectorcontrol means and the other valve operating said bounce air controlmeans, whereby the stroke of said pistons remains substantially consant.

8. A free piston compressor of the class described comprising axiallyaligned power, and bounce cylinders and pistons working therein, meansto control the quantity oi. fuel entering said power cylinder, means tovary the pressure of air in said bounce cylinders. each of said pistonscomprising a trunk portion between the power and compressor cylinders, arack connected to said trunk ortion of each piston and extending towardthe center of the compressor, a synchronizing pinion connecting each ofsaid racks, a mounting shaft for said pinion, a second pinion on saidmounting shaft, a rocking lever moved by said second pinion and havingabutting members at each end thereof, and spaced valves operated by saidabutting members at each end of the stroke of said locking lever, onevalve operating to actuate fuel control means and the other valveoperating said bounce air control means whereby the stroke of saidpistons remains substantially constant.

9. A free piston compressor of the class described comprising axiallyaligned power, compressor and bounce cylinders and pistons workingtherein, a fuel injector, fluid operated means to control said injectorto increase or decrease the quantity of fuel entering said powercylinder, means to vary the pressure of air in said bounce cylinders,each of said pistons comprising a trunk portion between the power andcompressor cylinders, a rack connected to said trunk portion of eachpiston and extending toward the center of the compressor, asynchronizing pinion connecting each of said racks, a mounting shaft forsaid pinion, a second pinion on said mounting shaft, a rocking levermoved by said second pinion and having abutting members at each endthereof, and spaced valves operated by said abutting members at each endof the stroke of said rocking lever, one valve operating to actuate fuelcontrol means and the other valve operating said bounce air controlmeans whereby the stroke of said pistons remains substantially constant.

10. A free piston compressor of the class described comprising axiallyaligned power, and bounce cylinders and pistons working therein, meansto control the quantity of fuel entering said power cylinder, a vent forsaid bounce cylinders, a source of high pressure air for said bouncecylinders, each of said pistons comprising a trunk portion between thepower and compressor cylinders, a rack connected to said trunk portionof each piston and extending toward the center of V the compressor, asynchronizing'pinion connecting each of said racks, a mounting shaft forsaid pinion, a second pinion on said mounting shaft, a rocking levermoved by said second pinion and having abutting members at each endthereof,

55 and spaced valves operated by said abutting members at each end ofthe stroke of said rocking lever, one valve operating to actuate fuelcontrol means and the other valve operating said bo air control meanswhereby the stroke of said so tons remains substantially constant.

, 11. A free piston compressor of the class described comprising axiallyaligned power, con;- pressor and bounce cylinders, and pistons workingtherein, a fuel injector, fluid operated means to control said injectorto increase or decrease the quantity of fuel entering said powercylinder, a vent for said bounce cylinders, a source of high pressureair for said bounce cylinders, fluid operated means to place said bouncecylinders either in communication with said vent to lower the pressuretherein or with said high prmnre air source to increase the pressuretherein, each of said pistons comprising a trunk portion between thepower and compressor cylinders, a rack iliconnectedtosaidtrunkportionofeachpiston eans and extending toward the center of the compressor, asynchronizing pinion connecting each of said racks, a mounting shaft forsaid pinion, a second pinion on said mounting shaft, a rocking levermoved by said second pinion and having abutting members at each endthereof, and spaced valves operated by said abutting members at each endof the stroke 01' said rocking lever, one valve operating to actuatefuel control means and the other valve operating said bounce air controlmeans whereby the stroke of said pistons remains substantially constant.

12. A tree piston compressor of the class described comprising axiallyaligned power, compressor and bounce cylinders, and pistons workingtherein, said compressor cylinder being closed at both ends and havingintake and exhaust valves at each side of the piston therein, acompressed air receiver in communication with one end of the compressorcylinder, a scavenging receiver header in communication with theopposite end oi said compressor cylinder, means to control the quantityof fuel entering said power cylinder, means to vary the pressure of airin REFERENCES CITED The following references are of record in the fileof patent:

UNITED STATES PATENTS Number Name Date 2,075,133 Pateras-Pescara Mar.30, 1937 2,200,892 Pateras-Pescara May 14, 1940 FOREIGN PATENTS NumberCountry Date 855,700 France 1939

